(CN) — The recent publicity surrounding the new images of space from the James Webb Space Telescope highlights the significance that telescopes themselves have in the pursuit of astronomy. A new paper released Thursday conceptualizes a telescope that can help us investigate the very earliest stages of the universe's development.
Researchers at the University of Cambridge in the U.K. have published a method that they hope will allow astronomers to peek past primordial gas clouds to detect light from the earliest stages of star and galaxy formation. Authors of the study propose that REACH (Radio Experiment for the Analysis of Cosmic Hydrogen) will represent a new frontier for telescopes investigating the origins of the stars.
In the decades since the adoption of the Big Bang as the prevailing theory for the creation of our universe, astronomers have tried to understand how the very first stars and galaxies formed out of the gaseous clouds that made up the universe at that point.
Observing this phenomenon has proven difficult, as the clouds of gases themselves are difficult to see through. The earliest epoch of our universe after the Big Bang is known as the "dark ages," a time where the universe was mainly made up of clouds of hydrogen and helium. REACH hopes to span this epoch and immediately afterward to the first light of the cosmic dawn and the beginning of reionization.
“Because of gravity, the elements eventually came together and the conditions were right for nuclear fusion, which is what formed the first stars. But they were surrounded by clouds of so-called neutral hydrogen, which absorb light really well, so it’s hard to detect or observe the light behind the clouds directly,” says lead author Eloy de Lera Acedo of Cambridge’s Cavendish Laboratory in a press release.
Observing this light behind the clouds relies upon the study of the 21-centimeter line, an electromagnetic radiation signature specific to the primordial hydrogen in the early universe.
The challenge of the 21-cm line arises from the relative weakness of the signal. It is also vulnerable to interference from stronger and closer radio signals, namely those from within our own galaxy. REACH aims to cut through any of this distortion to get a real look at the light from early cosmic structures.
“The primary science goal of REACH is noise-limited detection and observation of the evolution with redshift of the sky-averaged 21-cm hyperfine line emission from the neutral hydrogen that pervaded the intergalactic medium (IGM) during the cosmic dawn and the epoch of reionization. The extreme challenge posed by strong foreground emission necessitates exquisite instrument modelling and data calibration in global 21-cm experiments,” the study clarifies.
REACH is not the first experiment to measure the 21-cm signal for clues about first light, but it does exist as a reaction to previously published results, and to the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) in particular. The REACH team, a collaboration between Cambridge and The University of Stellenbosch in South Africa, was not entirely convinced by the results of EDGES, and conceived of REACH to investigate this doubt.
“The original result would require new physics to explain it, due to the temperature of the hydrogen gas, which should be much cooler than our current understanding of the Universe would allow. Alternatively, an unexplained higher temperature of the background radiation — typically assumed to be the well-known Cosmic Microwave Background — could be the cause,” de Lera Acedo says of the EDGES data.
Beyond these unusual reasonings, the data could even have been skewed by interference from other signals or systematic issues. Authors of the study offer REACH as a new methodology to eliminate the possibility of interferences and to specifically address the shortfalls in the EDGES data.
“In essence, we forgot about traditional design strategies and instead focused on designing a telescope suited to the way we plan to analyse the data — something like an inverse design. This could help us measure things from the Cosmic Dawn and into the epoch of reionization, when hydrogen in the Universe was reionized,” de Lera Acedo explains.
The paper details the simulations ran by the team to confirm the effectiveness of the process and the ongoing construction of the telescope. Rather than having one antenna like other radio telescopes, REACH will consist of two antennas to allow for simultaneous observations with a wider bandwidth to encompass a larger range of the cosmic timeline. This array of will allow them to minimize errors and more accurately analyze the multiple sources of data at the same time using Bayesian data analysis.
The telescope, located in the radio-quiet isolated Karoo desert in South Africa, is now just entering Phase I of its observations. The earliest reports are expected at the end of the year. The REACH team anticipates that Phase II will feature the incorporation of more complex antenna systems.
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